File extensions beginning with a

File Extension Description
A ADA source code file
A Library
A11 Graphics AIIM image file
A80 Assembler language source for 8080
AA, AB, ... Split parts of a single whole file
AAC Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio.
AAF AutoPatcher file
AAF Advanced Authoring Format is an advanced media wrapper file for professional applications.
AAS Animation Play Script
AB6 Datafile
AB8 Datafile
ABC Document
ABF Adobe Binary Screen Font
ABK Automatic backup file
ABM Image PALS album file
ABM Album file (various programs)
ABP Data
ABP AVS Barcode Profile
ABR Adobe Brush file for PhotoShop
ABS Abstracts (info file)
ABS Data file
AC Project backup
ACA Project
ACB Archive
ACC Program (DR-DOS - ViewMax)
ACE Archive
ACF Adobe Custom Filter for PhotoShop
ACL Project
ACL AutoCorrect List
ACM Audio Compression Module add-on
ACMB Graphics file
ACO Adobe Color Palette
ACT ACTOR source code file
ACT Animations Works Actor (Graphics cell)
ACT FoxDoc Action Diagrams
ACT Presentation
AD AfterDark screensaver module
AD2 ADPCM 2-bit compressed voice file
AD3 ADPCM 3-bit compressed voice file
ADA Ada source code file
ADB Ada Package Body
ADC Bitmap graphics (16 colors)
ADC Dictionary
ADD OS/2 adapter device driver
ADF Amiga Disk File
ADG Data
ADI Graphics file
ADI Database Index File
ADI Database Memo File
ADI Database Table
ADICHT LabChart data acquisition file
ADL MCA adapter description library
ADM After Dark support file
ADM ADEM file format
ADN Add-in
ADR After Dark support file
ADS Ada Package Specification
ADT WoW geographical map location file
ADT Datafile for cardfile application
ADT Dictionary
ADV GUS device driver
ADX Document
ADZ Amiga Disk Zipped (See Amiga Disk File)
AEP After Effects Project File
AF2 Flowchart
AF3 Flowchart
AFI Truevision bitmap graphics
AFL Font file (for Always)
AFM Datafile for cardfile application
AFM Type 1 font metric ASCII data for font installer
AFP Shape palette
AFT Template
AFW Workplace
AGR ArcView ASCII grid
AHK AutoHotkey script file
AI Vector graphics file
AIFC Audio Interchange File Format with Compression
AIFF Audio Interchange File Format
AiM Asm Text Mode Image File
AIN Archive
AIN Job schedule
AIO APL programming language file transfer format file
AIR Adobe AIR installation package
AIS Array of Intensity Samples graphics file
AIX Datafile for cardfile application
AKM "Akai Multitimbral" sample information file
AKP "Akai Program" sample information file
ALC Molecular coordinates
ALE Avid Log Exchange (used in film & video editing)
ALG Activity Log
ALL Arts & Letters symbol and font files
ALL Filelist w/ all files
ALL Format file for working pages
ALL General printer information
ALO Almanac support file
ALT Menu file
ALZ AlZip Compressed Files
AMD Maxum chromatograph offline database
AMF Music (Advanced Module Format)
AMG Archive
AMG System image file
AML AutomationML
AMR Audio format for mobile phones (Nokia, SonyEricsson)
AMS Adobe Monitor Setup calibration file
AMS Music format
ANA Lumina Decision Systems Analytica file
ANI Animation cursors for Win
ANI Animation
ANM Animation
ANN Help Annotations
Ann Multi volume ARJ archive
ANS ANSI character graphics (animation) file
ANS ASCII text ANSI character set
AOL America On-line for Windows DLL
AOS Add-On Software
AP Archive
AP Datafile
APC Printer driver
APD Printer driver
APE Monkey's Audio (Lossless)
APF Printer driver
API Adobe Printer Ink file for PhotoShop
API Passed parameter file
API Printer driver
APL APL work space format file
APL Support module used by Manugraphics APL products
APL EV-Dos Application File
APM Authorware Macintosh
APP Add-in application file
APP Application object file
APP Application
APP Application and Application Bundle
APP Executable workflow / macro file
APP Executable application file
APP Generated application
APR Employee performance review
APW Authorware Windows
APX Appexpert database file
AR Argon - for 3D Modeling
AR7 Archive
ARC Archive
ARC Archive
ARF Automatic Response File
ARH Archivers definitions file
ARI Archive
ARJ Archive
ARK ARC archive
ARK Archive
ARK Managing your Money Archive File
ARR Arrangement
ART Gerber artwork
ART First Publisher, Designworks, Greenstreet Draw graphic file
ART Graphics (scrapbook)
ART Graphics format (Another Ray Tracer)
ARTX file format
ARTX file format
ARX Archive
ASC ASCII text file
ASC Transport armor file
ASD Autosave file
ASD Presentation
ASD Screen driver
ASE Velvet Studio Sample
ASE ASCII Scene Export
ASF Datafile
ASF Screen font
ASF Advanced Streaming Format (Compressed Windows audio/video)
ASH Assembly language header file
ASI ASIC language source
ASI Assembler include file
ASK SYSGEN answer file
ASM Assembler language source
ASMX ASP.NET Web Service
ASO Assembler object (object-oriented) file
ASP ASPECT source code file
ASP Association of Shareware Professionals OMBUDSMN.ASP notice
ASP Active Server Pages of Microsoft.Net
ASPX ActiveX Server Pages of Microsoft.Net
ASS Amalgam Scene Specification
ASS Advanced SubStation Alpha (Subtitles)
AST Adobe Color Separation table for PhotoShop
ASW Authorware Star
ASX Advanced Stream Redirector file, redirects to an ASF file (see ASF)
ASZ Skin
AT2 Auto template
AT3 Atrac 3 Sound/music file
ATM Adobe Type Manager data/info
ATN Adobe Photoshop action
ATT AT&T Group
ATY Produced when an association type is exported by 3D Topicscape
AU Sun/NeXT/DEC Audio file
AU Sound (audio) file
AUD Audio file
AUP Audacity project file
AUX Auxiliary dictionary
AUX Auxiliary references
AUZ Ableton Live File
AVA Publication
AVB AntiViral Toolkit Pro Bases
AVI Audio Video Interleaved animation file
AVR Audio Visual Research
AVS Audio Video Software
AVT AVATAR-coding files
AW Text file
AWA Animations Works Accelerated Movie
AWD Microsoft Fax At Work Document
AWK AWK script/program
AWM Animations Works Movie (as .AVI)
AWS Data
Ax Directshow filter file format
AXF ARM Executable Image generated by the ARM tools.
AXM Axmedis object
AZD Amazon Software Download
AZW DRM enabled eBook
AZW1 DRM enabled eBook with embedded fonts
AZW2 Program file
AZZ Data file